Ca.sup.2+ channel blockers are widely used for the treatment of various cardiovascular disorders. Nifedipine, nitrendipine, nisoldipine, nimodipine and related 1,4-dihydropyridines (hereafter alternatively referred to as DHPs) are the most potent class of Ca.sup.2+ channel blockers. Radioreceptor and high performance liquid chromatography assays are available for the measurement of these agents in human serum, however, such techniques are cumbersome and costly and are not readily amenable to large-scale use.
The present invention provides immunogen conjugates comprising a DHP derivative coupled to immunogenic carrier materials and antibodies prepared against such immunogen conjugates. Such antibodies are useful in immunoassays for determining DHPs in biological fluids, thus filling the need for a rapid and sensitive assay for large-scale clinical use.